JP6137789B2 - Flat cable - Google Patents

Description

  The present invention relates to a thin flat cable that transmits a high-frequency signal.

  Conventionally, a coaxial cable has been used as a high-frequency line for transmitting a high-frequency signal. However, in recent years, with the reduction in size and thickness of high-frequency devices including mobile communication terminals, there is a problem that it is difficult to secure a space for arranging the coaxial cable in the terminal housing. Therefore, flat cables as shown in Patent Document 1 and Patent Document 2 have been proposed.

  The flat cables described in Patent Document 1 and Patent Document 2 have a flat shape whose thickness direction is thinner than the width direction. For this reason, even if it is a case where a coaxial cable cannot be arrange | positioned in the space between components or the space between components and a housing | casing in a terminal housing | casing, if it is a flat cable of patent document 1 and patent document 2, It can be arranged, and miniaturization of the device is not hindered.

  FIG. 9 is a diagram showing a configuration of a flat cable as shown in Patent Document 1 and Patent Document 2. The flat cable 1P is a flat cable that is thinner in the thickness direction than in the width direction, and FIG. 9 shows a partial configuration in the length direction. The flat cable 1P includes a base sheet made of a flexible insulating material such as polyimide or liquid crystal polymer. This base material sheet is omitted in FIG. The flat cable 1P includes a first ground conductor 10 and a second ground conductor 20 that are arranged with a base sheet sandwiched from the thickness direction and extend along the length direction of the flat cable 1P.

  The first ground conductor 10 is a so-called solid ground serving as a reference potential, and is a flat conductor. The second ground conductor 20 is a ladder-shaped flat conductor provided with a plurality of openings 20A formed along the length direction of the flat cable 1P. Specifically, the second ground conductor 20 includes the long conductors 21 and 22 arranged in parallel at a predetermined distance in the width direction of the flat cable 1P, and the erected conductor 23 that partially connects the long conductors 21 and 22. And. A plurality of installation conductors 23 are provided along the width direction of the flat cable 1P, and a plurality of installation conductors 23 are provided apart from each other along the length direction. The opening 20 </ b> A described above is a region surrounded by the long conductors 21 and 22 and the installation conductor 23.

  The flat cable 1P includes a central conductor 30A that is a signal line conductor of the flat cable 1P. The central conductor 30A is provided in the base sheet and is located between the long conductors 21 and 22 as viewed from the thickness direction of the base sheet. The first ground conductor 10 and the second ground conductor 20 are electrically connected through via-hole conductors 41 and 42 provided on the base sheet.

WO2011 / 007660 publication Utility Model Registration No. 3173143

  Incidentally, in the flat cable 1P shown in FIG. 9, in the region where the opening 20A is formed, a capacitor component is formed between the central conductor 30A and the long conductors 21 and 22, and this capacitor component is the flat cable 1P. Contributes to properties. For this reason, in order to make the flat cable 1P shown in FIG. 9 thinner, when the base sheet is made thin, in order to obtain the same characteristics, it is necessary to reduce the relative dielectric constant of the base sheet. In this case, the distance between the center conductor 30P and the second ground conductor 20 is reduced, and unnecessary radiation increases from the opening 20A.

  On the other hand, if the opening 20A is made small in order to suppress unnecessary radiation, the impedance of the opening 20A changes, so that the characteristics of the flat cable 1P are affected. Moreover, in order to suppress unnecessary radiation, when the relative dielectric constant of the base sheet is increased and the base sheet is thickened, the thickness of the flat cable 1P is increased, and the thinning cannot be realized.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a flat cable that can suppress unnecessary radiation without changing characteristics and can be made thin.

  A flat cable according to the present invention includes a first base sheet having a relative dielectric constant εr1, a long first ground conductor pattern formed on a first surface of the first base sheet, and the first base sheet. A second base sheet having a relative dielectric constant εr2 (> εr1) and a first base of the second base sheet, laminated on the second side of the sheet so that the second face thereof is opposed; A long second ground conductor pattern having a plurality of openings along the longitudinal direction and facing the first ground conductor pattern, and facing the first ground conductor pattern and opening of the second ground conductor pattern Is provided with a long signal transmission conductor pattern provided between the first base material sheet and the second base material sheet so as to overlap a part thereof.

  In this configuration, since the relative dielectric constant εr1 of the first base sheet is smaller than the relative dielectric constant εr2 of the second base sheet, the first base sheet has a first dielectric sheet that has a relative dielectric constant εr2, compared to a flat cable made of one base sheet. The thickness of the base sheet can be reduced. Thereby, thickness reduction is realizable in the whole flat cable. Moreover, since the relative dielectric constant εr2 of the second base material sheet on the opening side is larger than the relative dielectric constant εr1 of the first base material sheet, the second base material sheet does not become thin. For this reason, since the signal transmission conductor pattern is not too close to the opening, unnecessary radiation from the opening can be suppressed as compared with a flat cable made of one base sheet having a relative dielectric constant εr1.

  It is preferable that the first base sheet and the second base sheet have the same thickness.

  In this configuration, the signal transmission conductor pattern is located at substantially the same distance from both surfaces of the flat cable. For this reason, even if the flat cable is mountain-folded or valley-folded, the stress for bending is the same, so that the possibility of disconnection of the signal transmission conductor pattern can be reduced.

  According to the present invention, it is possible to realize a flat cable that can suppress unnecessary radiation without changing characteristics and can be made thinner as a whole.

FIG. 3 is an exploded perspective view of the flat cable according to the first embodiment. The figure which looked at the flat cable of FIG. 1 from the negative direction of the Z-axis. Sectional drawing of the III-III line of FIG. Sectional drawing of the IV-IV line of FIG. (A) is an external appearance perspective view of the connector cable which concerns on this embodiment, (B) is sectional drawing of a connector cable. (A) is side surface sectional drawing which shows the components structure of the portable electronic device which concerns on this embodiment, (B) is a plane sectional view explaining the component structure of the said portable electronic device. The disassembled perspective view of the flat cable in case a 1st base material sheet is a double-sided copper clad sheet and a 2nd base material sheet is a single-sided copper clad sheet. The disassembled perspective view of the flat cable in case a 1st base material sheet is a direction copper clad sheet and a 2nd base material sheet is a double-sided copper clad sheet. The figure which shows the structure of a flat cable as shown to patent document 1 and patent document 2. FIG.

(Embodiment 1)
FIG. 1 is an exploded perspective view of a flat cable according to the present embodiment. In FIG. 1, the X axis, the Y axis, and the Z axis are used to explain the X axis as the width direction of the flat cable 1, the Y axis as the length direction, and the Z axis as the thickness direction. Moreover, below, the same code | symbol is used about the same member as the flat cable 1P demonstrated in FIG.

  The flat cable 1 is configured by laminating a first ground conductor 10, a first base sheet 51, a central conductor 30, a second base sheet 52, and a second ground conductor 20 in order along the Z-axis direction. . The first base sheet 51 is a double-sided copper-clad sheet, and a first ground conductor pattern to be the first ground conductor 10 is formed on one surface (first surface), and the other surface (second surface). A central conductor pattern (signal transmission conductor pattern) to be the central conductor 30 is formed. Moreover, the 2nd base material sheet 52 is a single-sided copper clad sheet, and the 2nd ground conductor pattern used as the 2nd ground conductor 20 is formed in one surface. And the 1st substrate sheet 51 and the 2nd substrate sheet 52 are pasted together by thermocompression bonding.

  The first ground conductor 10, the central conductor 30, and the second ground conductor 20 are made of a highly conductive material such as copper (Cu). The 1st base material sheet 51 and the 2nd base material sheet 52 are insulating materials with heat flexibility, such as a liquid crystal polymer and polyimide, and are different in relative dielectric constant. When the relative dielectric constant εr1 of the first base sheet 51 and the relative dielectric constant εr2 of the second base sheet 52 are satisfied, the relation of εr2> εr1 is satisfied.

  The first ground conductor 10 is formed on one surface of the first base sheet 51 having the same shape, and has a strip shape that is long in the Y-axis direction, and is provided with rectangular connector portions 11 at both ends thereof. An opening 12 is formed in the connector 11, and a connector terminal 13 is formed in the opening 12. The connector terminal 13 is electrically connected to the central conductor 30 by a via hole conductor 45 formed in the first base sheet 51. For example, a coaxial connector or the like is attached to the connector portion 11. The coaxial connector is electrically connected to the central conductor 30 through the connector terminal 13 and the via hole conductor 45.

  The central conductor 30 is formed on the other surface of the first base sheet 51. The central conductor 30 is a long film extending along the Y axis, and is a flat film signal transmission line. The central conductor 30 has connector parts 33 provided at both ends in the Y-axis direction. The connector portion 33 is electrically connected to the connector terminal 13 of the first ground conductor 10 through the via hole conductor 45 described above.

  The second ground conductor 20 is formed on one surface of the second base sheet 52, has a strip shape that is long in the Y-axis direction, and has the same outer shape as the first ground conductor 10. The second ground conductor 20 has a plurality of openings 20A along the Y-axis direction. As described with reference to FIG. 9, the opening 20 </ b> A is formed by the long conductors 21 and 22 and the installation conductor 23. The second ground conductor 20 has a connector region opening 20 </ b> B formed in a region facing the opening 12 of the first ground conductor 10.

  The central conductor 30 may be provided on the other surface of the second base sheet 52.

  FIG. 2 is a view of the flat cable 1 of FIG. 1 viewed from the negative direction of the Z axis. The central conductor 30 overlaps with the opening 20A when viewed from the Z-axis direction, and is positioned substantially at the center of the opening 20A in the width direction (in the Z direction).

  The first base sheet 51 and the second base sheet 52 have substantially the same outer shape as the first ground conductor 10 and the second ground conductor 20. The first base sheet 51 and the second base sheet 52 are formed with via hole conductors 41, 42, 43, 44 that conduct the first ground conductor 10 and the second ground conductor 20. The via-hole conductors 41 and 42 are electrically connected to the vicinity of the installation conductor 23 of the first ground conductor 10 and the second ground conductor 20. The via-hole conductors 43 and 44 are electrically connected to the first ground conductor 10 and the vicinity of the connector region opening 20B. The first base sheet 51 is formed with a via-hole conductor 45 that conducts the connector terminal 13 of the first ground conductor 10 and the connector portion 33 of the central conductor 30.

  Note that a resist (not shown) is applied to the first ground conductor 10 and the second ground conductor 20.

  Hereinafter, the characteristic impedance of the flat cable 1 and unnecessary radiation from the opening 20A will be described. 3 is a cross-sectional view taken along line III-III in FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. Hereinafter, in the length direction (Y-axis direction) of the flat cable 1, the section in which the opening 20A is formed is referred to as section A (see FIG. 2), and the section in which the installation conductor 23 is formed is section B (see FIG. 2). 2).

  In section A, a capacitor component is formed between the central conductor 30 and the long conductors 21 and 22. The capacitor component formed at this time is lower than the capacitor component formed between the second ground conductor 20 and the second ground conductor 20 when there is no opening 20A. Therefore, the impedance of the flat cable 1 of the section A becomes higher (that is, becomes inductive) than the case where there is no opening 20A.

  In section B, a capacitor component is formed between the central conductor 30 and the erected conductor 23. The width of the installation conductor 23 is designed so that the capacitor component formed is higher than the capacitor component formed between the central conductor 30 and the long conductors 21 and 22. Thereby, the impedance of the flat cable 1 of the section B becomes lower than the impedance in the section A (that is, becomes capacitive).

  As described above, the characteristic impedance of the flat cable 1 is adjusted to a desired value by alternately providing the section A having a higher impedance and the section B having a lower impedance than the section A. For example, when the characteristic impedance of the flat cable 1 is adjusted to 50Ω, the impedance of the section A is set larger than 50Ω, the impedance of the section B is set smaller than 50Ω, and the entire length of the flat cable 1 (the above-described coaxial connector is mounted). Adjust between terminals to 50Ω.

  Further, the relative dielectric constant εr1 of the first base material sheet 51 is smaller than the relative dielectric constant εr2 of the second base material sheet 52. In the present embodiment, the relative permittivity εr1 = 2 and the relative permittivity εr2 = 3. Further, the thickness T1 of the first base sheet 51 and the thickness T2 of the second base sheet 52 are the same. Thereby, the flat cable 1 which concerns on this embodiment can make thickness thin compared with the flat cable (henceforth a 1st conventional type) which consists of one base material sheet whose relative dielectric constant is "3". Further, the flat cable 1 according to the present embodiment suppresses unnecessary radiation compared to a flat cable (hereinafter referred to as a second conventional type) made of one base sheet having a relative dielectric constant of “2”. it can.

  When the characteristic impedance of the first conventional type is set to 50Ω, it is assumed that T1 = 150 μm and T2 = 50 μm. When the relative permittivity is set to “2” in order to make the first conventional flat cable thin, in order to set the characteristic impedance of the second conventional flat cable to the same 50Ω, T1 = 100 μm, T2 = 33 μm. In this case, while the flat cable 1 can be made thin, the relative permittivity of the base sheet approaches “1”, and the central conductor 30 approaches the opening 20A, so that it is unnecessary from the opening 20A. Radiation increases or decreases. Further, if the opening 20A is made small in order to suppress radiation, the facing area between the central conductor 30 and the long conductors 21 and 22 becomes large, and the impedance of the opening 20A portion becomes small.

  In the present embodiment, by setting the relative dielectric constant εr1 of the first base sheet 51 on the first ground conductor 10 side to “2”, the thickness T1 of the first base sheet 51 is thinner than that of the first conventional type. it can. In addition, since the relative dielectric constant εr2 of the second base sheet 52 on the second ground conductor 20 side is set to “3”, the distance between the central conductor 30 and the long conductors 21 and 22 need not be reduced. The thickness T2 of the two base sheet 52 can be made the same as that of the first conventional type, and unnecessary radiation can be suppressed as compared with the second conventional type.

  Further, since the thickness T1 of the base sheet 51 and the thickness T2 of the second base sheet 52 are the same, the stress for bending is the same regardless of whether the flat cable 1 is mountain-folded or valley-folded. It becomes. For this reason, the possibility that the central conductor 30 is damaged during bending and the signal transmission line is disconnected can be reduced.

  As described above, the flat cable 1 according to the present embodiment includes the first base material sheet 51 and the second base material sheet 52 having different dielectric constants, thereby realizing a reduction in thickness and unnecessary from the opening 20A. Radiation can be suppressed.

  Moreover, when the flat cable 1 is bent and used by making the thickness T1 of the first base sheet 51 and the thickness T2 of the second base sheet 52 the same, disconnection of the central conductor 30 can be suppressed.

  The flat cable 1 according to this embodiment is manufactured in a two-stage process so that the characteristic impedance is 50Ω. First, a microstrip line composed of the first ground conductor 10, the first base sheet 51, and the central conductor 30 is manufactured so that the characteristic impedance becomes 50Ω or more. Thereafter, the second base sheet 52 on which the second ground conductor 20 is formed is laminated so that the characteristic impedance becomes 50Ω in total. That is, the first ground conductor 10 serves as a reference ground, and the second ground conductor 20 serves as an additional ground conductor for adjusting the characteristic impedance.

  In the present embodiment, the first base sheet 51 is a double-sided copper-clad sheet and the central conductor 30 is formed on the same sheet as the first ground conductor 10, but the second base sheet 52 is a double-sided copper-clad sheet. As an alternative, the central conductor 30 may be formed on the same sheet as the second ground conductor 20. In this case, the first base sheet 51 is a single-sided copper-clad sheet, and only the first ground conductor 10 is formed.

  The flat cable 1 manufactured as described above can be used for a connector cable as shown below. FIG. 5A is an external perspective view of the connector cable according to this embodiment, and FIG. 5B is a cross-sectional view of the connector cable.

  The connector cable 60 includes a flat cable 1 and a coaxial connector 61. The coaxial connectors 61 are disposed at both ends of the flat cable 1 in the longitudinal direction. Protective layers 120 and 130 are provided on the first ground conductor 10 and second ground conductor 20 sides, respectively. The coaxial connector 61 is installed on the surface of the protective layer 120 on the first ground conductor 10 side of the flat cable 1 via the conversion base 62. The central conductor of the coaxial connector 61 is connected to the central conductor 30 of the flat cable 1 through the via-hole conductor 45.

  With such a configuration, it is possible to realize a connector cable that is thin and flexible and has excellent transmission characteristics as a high-frequency line.

  The connector cable 60 having such a structure can be used for a portable electronic device as shown below. FIG. 6A is a side cross-sectional view illustrating a component configuration of the portable electronic device according to the present embodiment, and FIG. 6B is a plan cross-sectional view illustrating the component configuration of the portable electronic device.

  The portable electronic device 70 includes a thin device casing 71. In the device casing 71, mounted circuit boards 72A and 72B and a battery pack 73 are arranged. A plurality of IC chips 74 and mounting components 75 are mounted on the surfaces of the mounting circuit boards 72A and 72B. The mounting circuit boards 72A and 72B and the battery pack 73 are installed in the equipment casing 71 so that the battery casing 73 is disposed between the mounting circuit boards 72A and 72B in a plan view of the equipment casing 71. Here, since the device housing 71 is formed as thin as possible, the distance between the battery pack 73 and the device housing 71 is extremely narrow in the thickness direction of the device housing 71. Therefore, a coaxial cable cannot be arranged between them.

  However, the connector cable 60 shown in the present embodiment is arranged so that the thickness direction of the connector cable 60 and the thickness direction of the device housing 71 coincide with each other, so that the battery pack 73 and the device housing 71 are connected. A connector cable 60 can be passed between them. As a result, the mounted circuit boards 72A and 72B which are spaced apart from each other with the battery pack 73 disposed in the middle can be connected by the connector cable 60. This connector cable is used to connect the antenna element and the power feeding circuit.

(Embodiment 2)
Hereinafter, the flat cable which concerns on Embodiment 2 of this invention is demonstrated. In Embodiment 2, the 1st base material sheet 51 and the 2nd base material sheet 52 are polyimides, for example, and are pasted up via an adhesion layer.

  FIG. 7 is an exploded perspective view of a flat cable when the first base sheet 51 is a double-sided copper-clad sheet and the second base sheet 52 is a single-sided copper-clad sheet. In the case of the flat cable 1 </ b> A shown in FIG. 7, the adhesive layer 53 is preferably a material whose relative dielectric constant is smaller than the relative dielectric constant εr <b> 2 of the second base sheet 52. As a result, the relative permittivity on the second base sheet 52 side is reduced, and as a result of reducing the thickness of the second base sheet 52, it is possible to avoid the possibility that unnecessary radiation from the opening 20A cannot be suppressed.

  FIG. 8 is an exploded perspective view of a flat cable when the first base sheet 51 is a directional copper-clad sheet and the second base sheet 52 is a double-sided copper-clad sheet. In the case of the flat cable 1 </ b> B shown in FIG. 8, the adhesive layer 53 is preferably made of a material having a relative dielectric constant εr <b> 2 of the second base sheet 52. Thereby, the relative dielectric constant on the first base sheet 51 side is increased, and the thickness of the first base sheet 51 cannot be reduced, and as a result, it is possible to avoid the possibility that the flat cable 1A cannot be thinned.

  In the case of the flat cable shown in FIGS. 7 and 8, after the first base sheet 51 and the second base sheet 52 are bonded together, a hole is formed and the conductive paste is filled to form the via-hole conductor 41 and the like. The

  As described above, in the present embodiment, even when the first base sheet 51 and the second base sheet 52 are bonded to each other with the adhesive layer 53, the relative dielectric constant of the adhesive layer 53 is taken into consideration, so that the flatness is obtained. The cable 1A can suppress unnecessary radiation without changing the characteristics, and can be thinned.

  In addition, in the flat cable 1, about the interlayer connection conductor which conduct | electrically_connects the 1st ground conductor 10 and the 2nd ground conductor 20, when making it a via-hole conductor, it may be previously formed in the thermoplastic resin sheet before bonding. Alternatively, a hole may be formed, and after the sheets are bonded, the conductive paste may be filled. Alternatively, a through-hole type in which holes are formed after the sheets are bonded and a plating film or the like is provided on the inner peripheral surface of the holes may be used.

1-flat cable 10-first ground conductor 11-connector portion 12-opening 13-connector terminal 20-second ground conductor 21-long conductor 20A-opening 22-long conductor 23-installing conductor 30-center Conductor 31-wide part 32-narrow part 22-connector part 51-first base sheet 52-second base sheet 100-first roll part 101-double-sided copper-clad sheet 200-second roll part 201-single-sided copper Tension sheet 300-third roll part 301-synthetic sheet 401, 402-roll part

Claims (2)

A first substrate sheet having a relative dielectric constant εr1,
An elongated first ground conductor pattern formed on the first surface of the first base sheet;
A second substrate sheet laminated on the second surface side of the first substrate sheet so that the second surface thereof is opposed, and having a relative dielectric constant εr2 (>εr1);
An elongated second ground conductor pattern formed on the first surface of the second base sheet, having a plurality of openings along the longitudinal direction, and facing the first ground conductor pattern;
A length provided between the first base sheet and the second base sheet so as to face the first ground conductor pattern and so that an opening of the second ground conductor pattern overlaps a part thereof. A conductive pattern for signal transmission,
Flat cable with Have flexibility,
The first base sheet and the second base sheet have the same thickness,
The flat cable according to claim 1.

Images